Persistent halogenated organic pollutants (e.g., DDT, PCBs [polychlorinated biphenyls], dioxin) command special attention in public health because they are ubiquitous in the ecosystem and may be causing adverse human health effects at background levels of exposure, via diet. We are conducting several studies of the human health effects of background exposure to organochlorines. We have completed field work on a case-control study of serum p,p-DDE (a metabolite of DDT) and PCB levels in relation to risk of breast cancer among African-American women in Los Angeles. Three hundred cases and 300 controls have been enrolled, and the data will be prepared for analysis in 1999. Our main project is an investigation of health effects of in utero exposure to organochlorine residues among participants in the Collaborative Perinatal Project, for whom a specimen bank (mothers serum) is available. Associations being examined are: 1) mothers p,p-DDE levels in relation to risk of hypospadias, cryptorchidism, and polythelia in male offspring, 2) mothers PCB level in relation to childs neurodevelopmental outcomes, hearing, and IQ, 3) mothers DDE level in relation to body habitus in adolescence in male offspring. We are also examining in utero PCB exposure in relation to neonatal thryoid function in the North Carolina cohort study of effects of early-life organochlorine exposure (Rogan/Gladen study), and are collaborating with investigators from the Air Force Health Study to examine health effects of dioxin exposure. - PCBs, DDE, Cryptorchidism, Hypospadias, Breast neoplasms, Neurodevelopment, IQ, Thyroid - Human Subjects